From: Martin DeMello <martindemello@...>
Date: 2004-07-12T20:32:24+09:00
Subject: Re: A little algorithmic help requested...

Hal Fulton <hal9000@hypermetrics.com> wrote:
> Here's a problem my tired brain is having trouble with.
> 
> Given a sorted array of integers, convert them into as many
> ranges as possible (ranges of three or more).
> 
> Example:
> [1,2,3,4,6,7,8,11,12,15,16,17] ==> [1..4,6..8,11,12,15..17]
> 
> How would *you* do this?

a = [1,2,3,4,6,7,8,11,12,15,16,17]

i = 0; b = []
while (a[i]) do
  j = i
  while (a[j] && (a[j] - a[i]) == (j-i)) do
    j += 1
  end
  j = j-1
  b += ((j-i < 2) ? a[i..j] : [a[i]..a[j]])
  i = j+1
end

p b #=> [1..4, 6..8, 11, 12, 15..17]


martin